Zabbix - Track, record, alert and visualize performance and availability of IT resources
VOGSY - Professional service automation tool built on Google G Suite
openITCOCKPIT - openITCOCKPIT is a leading open source monitoring framework based on Naemon (Nagios). In addition it integrates Checkmk and Prometheus. It also offers interfaces to Icinga2, PRTG and opManager to obtain status and performance from them.
Timewatch - Timewatch offers time tracking, expense management, resource scheduling and professional services automation solutions.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
Krow - Krow Software is a professional service automation solution.